| Message ID | 20210322084135.17536-1-aardelean@deviqon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iio: buffer: return 0 for buffer getfd ioctl handler | expand |
On Mon, 22 Mar 2021 10:41:35 +0200 Alexandru Ardelean <aardelean@deviqon.com> wrote: > As Lars pointed out, we could either return the FD vs memcpy-ing it to the > userspace data object. > > However, this comment exposed a bug. We should return 0 or negative from > these ioctl() handlers. Because an ioctl() handler can also return > IIO_IOCTL_UNHANDLED (which is positive 1), which means that the ioctl() > handler doesn't support this ioctl number. Positive 1 could also be a valid > FD number in some corner cases. > > The reason we did this is to be able to differentiate between an error > code and an unsupported ioctl number; for unsupported ioctl numbers, the > main loop should keep going. > > Maybe we should change this to a higher negative number, to avoid such > cases when/if we add more ioctl() handlers. That sounds like a sensible follow up plan to me - perhaps we could use EOPNOTSUPP for this directly but add special handling for that in the core so it doesn't worry about it as long as someone supports the ioctl. > > Cc: Lars-Peter Clausen <lars@metafoo.de> > Fixes: f73f7f4da5818 ("iio: buffer: add ioctl() to support opening extra buffers for IIO device") > Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com> Applied to the togreg branch of iio.git and pushed out as testing. Thanks, Jonathan > --- > drivers/iio/industrialio-buffer.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c > index ee5aab9d4a23..d7a15c9bb0cd 100644 > --- a/drivers/iio/industrialio-buffer.c > +++ b/drivers/iio/industrialio-buffer.c > @@ -1442,7 +1442,7 @@ static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg > goto error_free_ib; > } > > - return fd; > + return 0; > > error_free_ib: > kfree(ib);
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index ee5aab9d4a23..d7a15c9bb0cd 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -1442,7 +1442,7 @@ static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg goto error_free_ib; } - return fd; + return 0; error_free_ib: kfree(ib);
As Lars pointed out, we could either return the FD vs memcpy-ing it to the userspace data object. However, this comment exposed a bug. We should return 0 or negative from these ioctl() handlers. Because an ioctl() handler can also return IIO_IOCTL_UNHANDLED (which is positive 1), which means that the ioctl() handler doesn't support this ioctl number. Positive 1 could also be a valid FD number in some corner cases. The reason we did this is to be able to differentiate between an error code and an unsupported ioctl number; for unsupported ioctl numbers, the main loop should keep going. Maybe we should change this to a higher negative number, to avoid such cases when/if we add more ioctl() handlers. Cc: Lars-Peter Clausen <lars@metafoo.de> Fixes: f73f7f4da5818 ("iio: buffer: add ioctl() to support opening extra buffers for IIO device") Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com> --- drivers/iio/industrialio-buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)